The impact of supplemental L-threonine in laying hen diets on egg component yield, composition, and functionality

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Abstract

The impacts of supplemental L-threonine in laying hen diets were evaluated.
Over three experiments, control hens were fed a corn-soybean commercial layer diet
containing 0.56% threonine (Thr). Experimental diets containing 0.66, 0.76, 0.86, and
0.96% Thr were fed for experiment 1. Experimental diets containing 0.76, 0.96 and
1.16% Thr were fed for experiment 2. Experiment 1 and 2 hens were 42 weeks of age.
In experiment 3, experimental diets containing 0.76 and 0.96% Thr were fed to aged
hens (61 weeks at beginning of experiment). Data collection methods were the same
for all three experiments. Beginning and ending hen weight, egg production, and feed
consumption data were collected. Egg samples were analyzed for egg weight, yolk and
albumen yield, protein, and functionality. In experiments 1 and 2, egg production
increased with increasing dietary threonine levels up to 0.76% Thr in the diet and
subsequently decreased suggesting a production threshold for the amino acid. Shell
cracking strength increased with increasing threonine levels in all three experiments. In
experiment 3, shell thickness increased with increasing threonine levels. Albumen
protein was significantly increased when hens were fed increased levels of dietary
threonine. Angel food cake volume was significantly increased in experiments 1 and 3 with increasing dietary threonine, as were other texture profile parameters. Sponge
cake volume was significantly increased in experiments 2 and 3 as a result of increased
threonine levels. In experiment 3, yolk gel hardness was significantly increased by
increasing the level of dietary threonine. These data clearly indicate a potential
important impact on egg composition and functionality by increasing dietary threonine
nutrition of a laying hen.